Field of the Invention
The present invention relates to a unit of connectors and a cable in which the connectors are connected with both ends of the cable, respectively, the unit having an arrangement such as to be used for balanced transmission. Hereinafter, such a unit will be referred to as a balanced-transmission cable-and-connector unit. In particular, the present invention relates to a balanced-transmission cable-and-connector unit used for connecting a computer with a peripheral device.
With the recent development of personal computers and networks thereof, systems are required for transmitting a large amount of data of, especially, dynamic images. In order to transmit a large amount of dynamic image data, it is necessary to transmit data at a high data transmission rate, not less than 1 gigabit/sec.
In the related art, unbalanced transmission is widely used in view of cost merit and so forth. However, because unbalanced transmission is likely to be affected by noise, it is considered that balanced transmission, which is less affected by noise, will be used in high-speed data transmission.
For connecting a personal computer with a peripheral device, a cable-and-connector unit, in which unit the connectors are connected with both ends of the cable, is used. It is therefore necessary to develop a cable-and-connector unit suitable for balanced transmission.
However, the cable-and-connector unit in the related art for connecting a personal computer with a peripheral device has a structure suitable for unbalanced transmission.
Thus, the cable-and-connector unit in the related art is not suitable for balanced transmission.
An object of the present invention is to provide a balanced-transmission cable-and-connector unit in which the problem described above is eliminated.
The above-mentioned object of the present invention is achieved by a balanced-transmission cable-and-connector unit which comprises:
a junction substrate;
a plug for balanced transmission connected to one end of the junction substrate;
a cable for balanced transmission connected to the other end of the junction substrate; and
a shielding cover covering the junction
substrate, a portion of the plug at which the plug is
connected to the junction substrate and a portion of the cable at which the cable is connected to the junction substrate, wherein:
the plug includes a pair of first and second signal contacts; and the length of a first signal transmitting path from the first signal contact to the cable via the junction substrate is substantially equal to the length
of a second signal transmitting path from the second signal contact to the cable via the junction substrate.
As a result of the length of the first signal transmitting path from the first signal contact to the cable via the junction substrate being substantially equal to the length of the second signal transmitting path from the second signal contact to the cable via the junction substrate, a time difference (skew) between a xe2x80x98+xe2x80x99 signal and a xe2x80x98xe2x88x92xe2x80x99 signal, which are transmitted in a manner of balanced transmission, does not occur, the magnitude of the xe2x80x98xe2x88x92xe2x80x99 signal being equal to the magnitude of the xe2x80x98+xe2x80x99 signal but the direction of the xe2x80x98xe2x88x92xe2x80x99 signal being reverse to the direction of the xe2x80x98+xe2x80x99 signal. As a result, the balanced-transmission cable-and-connector unit can be used for transmitting a high-speed signal of more than 1 gigabit/sec. with high reliability.
A balanced-transmission cable-and-connector unit, according to another aspect of the present invention, comprises:
a junction substrate;
a plug for balanced transmission connected to one end of the junction substrate;
a cable for balanced transmission connected to the other end of the junction substrate; and
a shielding cover covering the junction substrate, a portion of the plug at which the plug is connected to the junction substrate and a portion of the cable at which the cable is connected to the junction substrate,
wherein:
the plug includes a pair of first and second signal contacts;
the cable includes a plurality of sub-cables, the plurality of sub-cables being exposed from the end of the cable and connected to the end of the junction substrate; and
the length of a first signal transmitting path from the first signal contact to the cable via the junction substrate and an exposed sub-cable of the plurality of sub-cables is substantially equal to the length of a second signal transmitting path from the second signal contact to the cable via the junction substrate and another exposed sub-cable of the plurality of sub-cables.
As a result of the length of the first signal transmitting path from the first signal contact to the cable via the junction substrate and the exposed subcable of the plurality of sub-cables being substantially equal to the length of the second signal transmitting path from the second signal contact to the cable via the junction substrate and the other exposed sub-cable of the plurality of sub-cables, a time difference (skew) between the xe2x80x98+xe2x80x99 signal and the xe2x80x98xe2x88x92xe2x80x99 signal, which are transmitted in the manner of balanced transmission, does not occur. As a result, the balanced-transmission cable-and-connector unit can be used for transmitting a high-speed signal of more than gigabit/sec. with high reliability.
A balanced-transmission cable-and-connector unit, according to another aspect of the present invention, comprises:
a junction substrate;
a plug for balanced transmission connected to one end of the junction substrate;
a cable for balanced transmission connected to the other end of the junction substrate; and
a shielding cover covering the junction substrate, a portion of the plug at which the plug is connected to the junction substrate and a portion of the cable at which the cable is connected to the junction substrate,
wherein:
the plug comprises a housing made of synthetic resin and alternately arranged ground contacts and pairs of signal contacts, each pair of the pairs of signal contacts having first and second leg portions between which the end of the junction substrate is inserted, the lengths of the first and second leg portions of each pair of the pairs of signal contacts being equal to one another;
the cable comprises a tube-shaped outer covering portion, a tube-shaped sub-cable shielding portion provided inside the outer covering portion, a plurality of sub-cables circularly arranged along the inner surface of the sub-cable shielding portion and a filler portion filling a portion of the cable inside the plurality of sub-cables, each of the plurality of sub-cables comprising a pair of leads for balanced transmission and a lead shielding portion shielding the pair of leads;
the junction substrate has a multi-layer structure and has ground lands on the obverse surface and the reverse surface at one end thereof, the lead shielding portions being soldered to the ground lands, the junction substrate further having pairs of signal pads on the obverse surface and the reverse surface at the other end thereof, each pair comprising one pad on the obverse surface and the other on the reverse surface, the junction substrate further having pairs of lead connection pads on the obverse surface and the reverse surface thereof between the ground lands and the pairs of signal pads, each pair of the pairs of signal pads having the leads of the respective one of the plurality of sub-cables soldered thereto, the junction substrate further having first wiring connecting one pad of each pair of the pairs of lead connection pads with the obverse-surface-side pad of the respective pair of the pairs of signal pads using an internal layer of the junction substrate and second wiring connecting the other pad of each pair of the pairs of lead connection pads with the reverse-surface-side pad of the respective pair of the pairs of signal pads using another internal layer of the junction substrate, the length of the first wiring being substantially equal to the length of the second wiring;
the first and second leg portions of each pair of the pairs of signal contacts of the plug has the junction substrate inserted therebetween, and two leg portions of each of the ground contacts of the plug has the junction substrate inserted therebetween, the first leg portion of each pair of the pairs of signal contacts being soldered to the obverse-surface-side pad of the respective pair of the pairs of signal pads and the second leg portion of each pair of the pairs of signal contacts being soldered to the reverse-surface-side pad of the respective pair of the pairs of signal pads, thus the plug being connected with the end of the junction substrate;
the plurality of sub-cables exposed from the end of the cable are equally separated into sub-cables on the obverse-surface side of the junction substrate and sub-cables on the reverse-surface side of the junction substrate, the pair of leads of each of the plurality of sub-cables being soldered to the respective pair of the pairs of lead connection pads, respectively; and
the shielding cover has shielding-plate portions at one end thereof and shielding-arm portions at the other end thereof, the shielding-plate portions being inserted into the plug and the shielding-arm portions being connected with the sub-cable shielding portion of the cable, thus the shielding cover being fastened to the plug and the cable.
Because the junction substrate has the multi-layer structure, and the first wiring and the second wiring use the internal layers, it is possible that the length of the first wiring is approximately equal to the length of the second wiring. Further, the sub-cables of the cable are arranged circularly, and also, the sub-cables exposed from the end of cable are equally separated into the sub-cables on the obverse-surface side of the junction substrate and the reverse-surface side of the junction substrate. As a result, it is possible that the lengths of the sub-cables exposed from the end of the cable are approximately equal to each other. Thereby, a time difference (skew) between the xe2x80x98+xe2x80x99 signal and the xe2x80x98xe2x88x92xe2x80x99 signal, which are transmitted in the manner of balanced transmission, does not occur. Further, a time difference (skew) between the signals transmitted through the plurality of sub-cables does not occur. As a result, the balanced-transmission cable-and-connector unit can be used for transmitting a high-speed signal of more than gigabit/sec. with high reliability.
Further, the shielding-plate portions are portions of the shielding cover and are not separate parts. Therefore, it is not necessary to increase the number of parts.
A plug for balanced transmission, according to the present invention, comprises:
a housing made of synthetic resin;
alternately arranged ground contacts and pairs of signal contacts; and
two shielding plates incorporated into the housing oppositely,
wherein:
each pair of the pairs of signal contacts has first and second leg portions between which an end of a printed-circuit board is inserted, the lengths of the first and second leg portions of each pair of the pairs of signal contacts being equal to one another; each of the ground contacts has leg portions between which the end of the printed-circuit board is inserted; and the two shielding plates have leg portions between which the end of the printed-circuit board is inserted.
Because each pair of the pairs of signal contacts has first and second leg portions between which the end of the printed-circuit board is inserted, it is possible that the plug for balanced transmission is connected to the printed-circuit board in a manner in which the printed-circuit board is located on the center line of the plug. Thereby, a time difference (skew) between the xe2x80x98+xe2x80x99 signal and the xe2x80x98xe2x88x92xe2x80x99 signal, which are transmitted in the manner of balanced transmission, does not occur.
A plug for balanced transmission, according to another aspect of the present invention, comprises:
a housing made of synthetic resin;
alternately arranged ground contacts and pairs of signal contacts; and
two shielding members inserted into the housing oppositely,
wherein:
each pair of the pairs of signal contacts has first and second leg portions between which an end of a printed-circuit board is inserted, the lengths of the first and second leg portions of each pair of the pairs of signal contacts being equal to one another;
each of the ground contacts has leg portions between which the end of the printed-circuit board is inserted; and
the two shielding members have shielding plate portions which are inserted into the housing, and covering portions which cover the first and second leg portions of each pair of the pairs of signal contacts and the leg portions of each of the ground contacts when the shielding-plate portions are inserted into the housing.
Because each pair of the pairs of signal contacts has first and second leg portions between which the end of the printed-circuit board is inserted, it is possible that the plug for balanced transmission is connected to the printed-circuit board in a manner in which the printed-circuit board is located on the center line of the plug. Thereby, a time difference (skew) between the xe2x80x98+xe2x80x99 signal and the xe2x80x98xe2x88x92xe2x80x99 signal, which are transmitted in the manner of balanced transmission, does not occur.
Further, because the first and second leg portions of each pair of the pairs of signal contacts and the leg portions of each of the ground contacts are covered by the covering portions of the shielding members, the first and second leg portions of each pair of the pairs of signal contacts and the leg portions of each of the ground contacts are not likely to be affected by external electromagnetic noise.
Other objects and further features of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.